KRAS and colonic neoplasm: We first examined the validity of the pyrosequencing method using eleven colon cancer tissues harboring 4 different KRAS mutations [c.35G>T (codon 12 GGT>GTT; p.Gly12Val), c.35G>A (codon 12 GGT>GAT; p.Gly12Asp), c.34G>T (codon 12 GGT>TGT; p.Gly12Cys), and c.38G>A mutation (codon 13 GGC>GAC; p.Gly13Asp)].